1. Field of the Invention
The present invention relates to a brake hose, such as an oil pressure hose, or the like, having reinforcing thread layers braided intermediately for use in a flow path for a pressure fluid.
The present application is based on Japanese Patent Application No. Hei. 10-230341, which is incorporated herein by reference.
2. Description of the Related Art
Heretofore, for example, a brake hose shown in FIG. 8 is known as brake hose of this type. FIG. 8 is a sectional view showing a brake hose 100. The brake hose 100 is constituted by lamination of an inner tube layer 102, a lower thread layer 104, an intermediate rubber layer 106, an upper thread layer 108 and a skin rubber layer 110 successively in outward order from a flow path 101 for making an operating fluid flow. To produce the brake hose 100, first, an EPDM rubber material is extrusion-molded annularly to form the inner tube layer 102. Lower threads are then braided by a braider to form the lower thread layer 104. A sheet-like rubber material is then wound on the lower thread layer 104. Upper threads are then braided to form the upper thread layer 108. A dipping process is then carried out so that an adhesive agent is applied onto the upper thread layer 108. After the adhesive layer is dried, a rubber material is extruded onto the upper thread layer 108 to thereby laminate the skin rubber layer 110 on the upper thread layer 108. Further, a vulcanizing process and a predetermined after-process are carried out to thereby complete the brake hose 100. In the brake hose 100, the two layers, that is, the lower and upper thread layers 104 and 108 are buried in a rubber base in order to enhance pressure resistance. Furthermore, the adhesive agent layer 109 is applied onto the upper thread layer 108 to thereby enhance the bonding strength between the upper thread layer 108 and the skin rubber layer 110 to thereby enhance the pressure resistance.
Although the adhesive agent layer 109 has an effect of enhancing the bonding strength of the upper thread layer 108, etc. on one hand, the adhesive agent layer 109 makes the stiffness of the brake hose 100 per se high on the other hand. If the stiffness of the brake hose 100 is made high, it becomes difficult to bend the brake hose 100 smoothly in response to the motion of a tire. There was a problem that durability was spoiled.
In the case where the amount of application of the adhesive agent layer is reduced to decrease the stiffness to cope with the aforementioned problem, the amount of volume expansion of the brake hose 100 increases to spoil the brake feeling when the pressure of an operating fluid is applied to the inside of the brake hose 100. Thus, durability decreases as the stiffness of the brake hose 100 increases, while the amount of volume expansion of the brake hose 100 increases to spoil the brake feeling as the stiffness decreases. There was therefore a problem that it was difficult to make the two consistent with each other.